Polymers prepared from 2-(3-aminophenyl)-2-(4-aminophenyl) hexafluoro propane

ABSTRACT

Polyimides and polyamide-acids having improved solubility and processing characterisitcs are provided having incorporated into the polymeric chain as a novel aromatic diamine compound, 2-(3-aminophenyl)-2-(4-aminophenyl) hexafluoropropane (3,4&#39;-6F Diamine). The polyamide-acids and polyimides are prepared by reacting the 3,4&#39;-6F Diamine with aromatic tetracarboxylic acids or anhydrides thereof. It has been found that the polyimides of this invention have improved solubility characterisitics, low dielectric constants and improved thermal flow properties as a consequence of the meta/para positioning of the amino groups on the diamine, which renders these polymers more readily melt spinnable for the production of fibers. The polymers may also be compression molded and fabricated into composites at moderate temperatures and pressures. Solutions of the polyimides may be cast into films.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to new fluorine-containing polyimides andpolyamide-acids which exhibit improved solubility in common organicsolvents, low dielectric constants and improved thermal flow properties.

2. Description of Related Art

Polyimides are widely used in the aerospace industry and electronicsindustry, because of their toughness, low density, thermal stability,radiation resistance and mechanical strength. However, it is recognizedthat polyimides are difficult to process. The processing problems arisefrom the insolubility of polyimides in most of the more common solvents.Consequently, products have been fabricated from polyamide-acidintermediates, which are more soluble but less stable, and then imidizedby the application of heat to provide the desired end product. Thedisadvantage of this process is that the water liberated during theimidization of the polyamide-acid forms undesirable voids or surfaceirregularities in the final product which reduces its mechanicalproperties.

It has been suggested that polyimides having hexafluoroisopropylidenelinking group in the diamine and/or dianhydride comonomers have improvedsolubility properties. Several patents disclose polyimides prepared fromdiamines of this type. For example, U.S. Pat. No. 3,356,648 to Rogersdiscloses polyimides prepared from 2,2-bis(4-aminophenyl)hexafluoropropane; U.S. Pat. No. 4,592,925 to DuPont et al. disclosespolyimides prepared from 2,2-bis(3-aminophenyl) hexafluoropropane; U.S.Pat. No. 4,111,906 to Jones et al. discloses polyimides prepared from2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane; and U.S. Pat. No.4,477,648 to Jones et al. discloses polyimides prepared from2,2-bis[(2-halo-4-aminophenoxy)phenyl]hexafluoropropane. In addition,U.S. Pat. No. 4,592,925 discloses polyimides prepared by reacting2,2-bis(3-aminophenyl) hexafluoropropane and4,4,-hexafluoroispropylidenebis (phthalic anhydride), also known as2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride.

It is also known in the art to prepare polyamides by condensing amixture of diamines, including a 3,4'-diamino diphenyl compound, with adicarboxylic acid, such as disclosed in U.S. Pat. No. 4,075,172. Similarpolyamides are suggested in U.S. Pat. No. 3,792,148. However, neither ofthese patents suggests polyamides or polyimides containing thehexafluoroisopropylidene group.

SUMMARY OF THE INVENTION

The present invention provides polyimides and polyamide-acids havingimproved solubility and processing characteristics having incorporatedinto the polymeric chain the novel aromatic diamine compound2-(3-aminophenyl)-2-(4-aminophenyl) hexafluoropropane, hereinafterreferred to as meta/para-6F Diamine or 3,4'-6F Diamine. Thepolyamide-acids and polyimides are prepared by reacting the 3,4'-6FDiamine with aromatic tetracarboxylic acids or anhydrides thereof. Ithas been found that the polyimides of this invention have improvedsolubility characteristics, low dielectric constants and improvedthermal flow properties as a consequence of the meta/para positioning ofthe amino groups on the diamine, which renders these polymers morereadily melt spinnable for the production of fibers. The polymers mayalso be compression molded and fabricated into composites at moderatetemperatures and pressures.

DETAILED DESCRIPTION OF THE INVENTION

The polyimides of this invention may be characterized as comprised ofrecurring groups having the structure: ##STR1## wherein n is the numberof repeating groups, R is a tetravalent aromatic organic radical whereineach pair of carbonyl groups are attached to adjacent carbons in thering of moiety R, and Q is the imidized residuum of2-(3-aminophenyl)-2-(4-aminophenyl) hexafluoropropane having theformula: ##STR2## Preferably R in formula 1 comprises a phenylene,naphthalene or a bis-phenylene type compound, or a mixture of suchcompounds, all of which may be unsubstituted or substituted withhalogen, hydroxy, lower C₁ to C₆ alkyl or lower C₁ -C₆ alkoxy groups,and n is a number sufficient to provide an inherent viscosity of atleast about 0.2 dl/g as measured from a solution of the polymer indimethylacetamide at 25° C. at a polymer concentration of 0.5 weightpercent.

Illustrative of tetracarboxylic acid dianhydrides which are suitable foruse in the present invention are:

1,2,4,5-benzene tetracarboxylic acid dianhydride;

1,2,3,4-benzene tetracarboxylic acid dianhydride;

1,4-bis(2,3-dicarboxyphenoxy) benzene dianhydride;

1,3-bis(3,4-dicarboxyphenoxy) benzene dianhydride;

1,2,4,5-naphthalene tetracarboxylic acid dianhydride;

1,2,5,6-naphthalene tetracarboxylic acid dianhydride;

1,4,5,8-naphthalene tetracarboxylic acid dianhydride;

2,3,6,7-naphthalene tetracarboxylic acid dianhydride;

2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride;

2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride;

2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic acid dianhydride;

3,3',4,4'-diphenyl tetracarboxylic acid dianhydride;

2,2',3,3'-diphenyl tetracarboxylic acid dianhydride;

4,4'-bis(3,4-dicarboxyphenoxy)diphenyl dianhydride;bis(2,3-dicarboxyphenyl) ether dianhydride;

4,4'-bis(2,3-dicarboxyphenoxy) diphenyl ether dianhydride;

4,4'-bis(3,4-dicarboxyphenoxy) diphenyl ether dianhydride;

bis(3,4-dicarboxyphenyl) sulfide dianhydride; dianhydride;

4,4'-bis(3,4-dicarboxyphenoxy) diphenyl sulfide dianhydride;

bis(3,4-dicarboxyphenyl) sulfone dianhydride;

4,4'-bis(2,3-dicarboxyphenoxy) diphenyl sulfone dianhydride;

4,4'-bis(3,4-dicarboxyphenoxy) diphenyl sulfone dianhydride;

3,3',4,4'-benzophenone tetracarboxylic acid dianhydride;

2,2',3,3'-benzophenone tetracarboxylic acid dianhydride;

2,3,3'4'-benzophenone tetracarboxylic acid dianhydride;

4,4'-bis(3,4-dicarboxyphenoxy) benzophenone dianhydride;

bis(2,3-dicarboxyphenyl) methane dianhydride;

bis(3,4-dicarboxyphenyl) methane dianhydride;

1,1-bis(2,3-dicarboxyphenyl) ethane dianhydride;

1,1-bis(3,4-dicarboxyphenyl) ethane dianhydride;

1,2-bis(3,4-dicarboxyphenyl) ethane dianhydride;

2,2-bis(2,3-dicarboxyphenyl) propane dianhydride;

2,2-bis(3,4-dicarboxyphenyl) propane dianhydride;

2,2-bis[4-(2,3-dicarboxyphenoxy) phenyl]propane dianhydride;

2,2-bis[4-(3,4-dicarboxyphenoxy) phenyl]propane dianhydride;

4-(2,3-dicarboxyphenoxy)-4,-(3,4-dicarboxyphenoxy) diphenyl-2,2-propanedianhydride;

2,2-bis[4-(3,4-dicarboxyphenoxy-3,5-dimethyl) phenyl]propanedianhydride;

2,3,4,5-thiophene tetracarboxylic acid dianhydride;

2,3,4,5-pyrrolidine tetracarboxylic acid dianhydride;

2,3,5,6-pyrazine tetracarboxylic acid dianhydride;

1,8,9,10-phenanthrene tetracarboxylic acid dianhydride;

3,4,9,1-perylene tetracarboxylic acid dianhydride;

2,2-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride;

1,3-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride;

1,1-bis(3,4-dicarboxyphenyl)-1-phenyl-2,2,2-trifluoroethane dianhydride:

2,2-bis[4-(3,4-dicarboxyphenoxy) phenyl]hexafluoropropane dianhydride:

1,1-bis[4-(3,4-dicarboxyphenoxy) phenyl]-1-phenyl-2,2,2-trifluoroethanedianhydride; and

4,4'-bis[2-(3,4-dicarboxyphenyl)hexafluoroisopropyl]diphenyl etherdianhydride.

One skilled in the art will recognize that the tetracarboxylic acids andacid-esters of the above-listed dianhydride compounds may also be usedto produce the polyimides. These tetracarboxylic acids or derivativesthereof are available or may be prepared by known methods. For example,U.S. Pat. No. 3,847,867 to Heath et al. and U.S. Pat. No. 4,650,850 toHowson, which are incorporated herein by reference, show the preparationof bis(ether anhydrides) and bis(dialkyl aromatic ether anhydrides),respectively. The preparation of fluorine-containing dianhydrides isdisclosed in U.S. Pat. No. 3,310,573 to Gordon and U.S. Pat. No.3,649,601 to Critchley et al., which are also incorporated herein byreference.

The preferred polyimides of this invention are prepared by reacting the3,4,-6F Diamine with 1,2,4,5-benzene tetracarboxylic acid dianhydride(also known as pyromelittic dianhydride-PMDA), bis(3,4-dicarboxyphenyl)ether dianhydride (also known as oxyphthalic dianhydride-ODPA),3,3',4,4'-benzophenone tetracarboxylic acid dianhydride (also known asbenzo phenonetetracarboxylic dianhydride-BTDA), 3,4',4,4'-diphenyltetracarboxylic acid dianhydride (BPDA), 2,2-bis(3,4dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), and 4,4'-bis[2-(3,4dicarboxyphenyl) hexafluoroisopropyl]diphyenyl ether dianhydride (12FDA).

Polyimides of the present invention may also be prepared using a mixtureof 3,4'-6F Diamine and one or more other diamines having the formula:

    NH.sub.2 --Y--NH.sub.2                                     ( 3)

wherein Y is an aromatic moiety of a phenylene naphthalene orbis-phenylene type compound which may be unsubstituted or ringsubstituted with halogen, hydroxy, lower C₁ to C₆ alkyl or lower C₁ toC₆ alkoxy groups. Where such diamine mixtures are employed, the molarratio of 3,4'-6F Diamine and said one or more other diamines ispreferably within the range of about 2 to 1 to about 1 to 2 based on thetotal moles of diamine present.

Illustrative of diamines which are suitable for use in mixtures with3,4'-6F Diamine are:

m-phenylene diamine;

p-phenylene diamine;

1,3-bis(4-aminophenyl) propane;

2,2-bis(4-aminophenyl) propane;

4,4'-diamino-diphenyl methane;

1,2-bis(4-aminophenyl) ethane;

1,1-bis(4-aminophenyl) ethane;

2,2'-diamino-diethyl sulfide;

bis(4-aminophenyl) sulfide;

2,4'-diamino-diphenyl sulfide;

bis(3-aminophenyl)sulfone;

bis(4-aminophenyl) sulfone;

4,4'-diamino-dibenzyl sulfoxide;

bis(4-aminophenyl) ether;

bis(3-aminophenyl) ether;

bis(4-aminophenyl)diethyl silane;

bis(4-aminophenyl) diphenyl silane;

bis(4-aminophenyl) ethyl phosphine oxide;

bis(4-aminophenyl) phenyl phosphine oxide;

bis(4-aminophenyl)-N-phenylamine;

bis(4-aminophenyl)-N-methylamine;

1,2-diamino-naphthalene;

1,4-diamino-naphthalene;

1,5-diamino-naphthalene;

1,6-diamino-naphthalene;

1,7-diamino-naphthalene;

1,8-diamino-naphthalene;

2,3-diamino-naphthalene;

2,6-diamino-naphthalene;

1,4-diamino-2-methyl-naphthalene;

1,5-diamino-2-methyl-naphthalene;

1,3-diamino-2-phenyl-naphthalene;

4,4'-diamino-biphenyl;

3,3'-diamino-biphenyl;

3,3'-dichloro-4,4'-diamino-biphenyl;

3,3'-dimethyl-4,4'-diamino-biphenyl;

3,4'-dimethyl-4,4'-diamino-biphenyl;

3,3'-dimethoxy-4,4'-diamino-biphenyl;

4,4'-bis(4-aminophenoxy)-biphenyl;

2,4-diamino-toluene;

2,5-diamino-toluene;

2,6-diamino-toluene;

3,5-diamino-toluene;

1,3-diamino-2,5-dichloro-benzene;

1,4-diamino-2,5-dichloro-benzene;

1-methoxy-2,4-diamino-benzene;

1,4-diamino-2-methoxy-5-methyl-benzene;

1,4-diamino-2,3,5,6-tetramethyl-benzene;

1,4-bis(2-methyl-4-amino-pentyl)-benzene;

1,4-bis(1,1-dimethyl-5-amino-pentyl)-benzene;

1,4-bis(4-aminophenoxy)-benzene;

o-xylylene diamine;

m-xylylene diamine;

p-xylylene diamine;

3,3'-diamino-benzophenone;

4,4'-diamino-benzophenone;

2,6-diamino-pyridine;

3,5-diamino-pyridine;

1,3-diamino-adamantane;

3,3'-diamino-1,1,1'-diadamantane;

N-(3-aminophenyl)-4-aminobenzamide;

4-aminophenyl-3-aminobenzoate;

2,2-bis(4-aminophenyl) hexafluoropropane;

2,2-bis(3-aminophenyl) hexafluoropropane;

2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane;

2,2-bis[4-(2-chloro-4-aminophenoxy)phenyl hexafluoropropane;

1,1-bis(4-aminophenyl)-1-phenyl-2,2,2-trifluoroethane;

1,1-bis[4-(4-aminophenoxy)phenyl]-1-phenyl-2,2,2-trifluoroethane;

1,4-bis(3-aminophenyl)buta-1-ene-3-yne;

1,3-bis(3-aminophenyl) hexafluoropropane;

1,5-bis(3-aminophenyl) decafluoropentane; and mixtures thereof.

A preferred process for preparing the polyimides of this inventioninvolves first preparing a polyamide-acid by reacting the diamine andthe tetracarboxylic acid or derivative such as the dianhydride in anorganic solvent, preferably under substantially anhydrous conditions fora time and at a temperature sufficient to provide at least 50% of thecorresponding polyamide-acid, and then converting the polyamide-acid tothe polyimide. Suitable conditions for reacting the diamine and thedianhydride are disclosed in detail in U.S. Pat. Nos. 3,356,648 and3,959,350, both to Rogers, which are incorporated herein by reference.The intermediate polyamide-acid may also be esterified to providepolyamide-esters.

In a preferred process for preparing the polyimides, electronic gradediamine and dianhydride may be reacted in N-methyl pyrrolidone,gamma-butyrolactone (BLO), or a mixture of BLO and another solvent suchas diglyme. The resulting product is a polyamide-acid which is thenconverted to the desired polyimide by one of several methods: heatingthe polyamide-acid solution until imidization is substantially complete,or by combining the polyamide-acid solution and a dehydrating agent,with or without catalyst, and optionally heating the resulting mixtureuntil imidization is substantially complete.

In the preferred embodiment of the invention, the diamine and thedianhydride components are reacted in approximately equi-molar amounts.

The following examples are illustrative of the invention.

EXAMPLE 1

2-(3-aminophenyl)-2-(4-aminophenyl)hexafluoropropane monomer wasprepared by a six step process employing2-(4-methylphenyl)hexafluoropropane-2-ol and benzene as startingmaterials as follows:

(a) Preparation of 2-(4-Methylphenyl)-2-phenylhexafluoropropane.

1290 g of 2-(4-methylphenyl)hexafluoropropan-2-ol and 780 g of benzenewere placed in a 5-liter steel autoclave and 1500 g of anhydroushydrogen fluoride was pumped into the sealed autoclave. The reactionmixture was heated at 170°-175° C. with stirring for 64 hours. Aftercompletion of the reaction, hydrogen fluoride gas was allowed to escapeat 80° C., and the liquid product was then washed twice with water,dried over calcium chloride, and fractionally distilled. Boiling point135°-136° C./1.4 mbar. Yield: 1424 g (89.5%).

(b) Preparation of 2-(4-Carboxyphenol)-2-phenylhexafluoropropane

298 g of 2-(4-methylphenyl)-2-phenylhexafluoropropane prepared in step(a), 2.49 g of cobalt (II) acetate tetrahydrate, 2.45 g of manganese(IV) acetate tetrahydrate, and 0.41 g of hydrogen bromide (correspondingto 4.1 g of a 10% HBr solution in glacial acetic acid) were placed in a1-liter glass autoclave. The mixture was heated under an oxygen pressureof 6.5 bar up to approximately 180° C. with an exothermic reaction, andwas allowed to stand for 1 hour at 170°-180° C. 200 g of acetic acid wasthen distilled from the reaction solution cooled to approximately 100°C. 275 g of water was added slowly to the solution remaining in theflask (approximately 600 g) at the boiling point. The carboxylic acidthat crystallized out was filtered by suction and washed twice with75-ml portions of 50% aqueous acetic acid and five times with 85-mlportions of water, and was dried at 60° C./60 mbar. Yield: 311 g(95.5%).

(c) preparation of2-(4-carboxyphenol)-2-(3-nitrophenyl)hexafluoropropane

261 g of 2-(4-carboxyphenyl)-2-phenylhexafluoropropane prepared in step(b) was suspended in 500 ml of methylene chloride, and after theaddition of 188 ml of concentrated sulfuric acid, 75 ml of concentratednitric acid was added dropwise at -5° to 0° C. The reaction mixture wasstirred for 1 hour longer at this temperature and was then poured onto2000 g of ice. The solid was filtered off and washed with water untilthe rinse water had a pH of 3-4. Crude product 208 g, M.p. 180°-185° C.Workup of the filtrate: The organic phase was separated, washed twicewith water, dried over magnesium sulfate, and evaporated. The stickyyellow residue was recrystallized twice from toluene, after which anadditional 30 g of crude product was obtained with a melting point of180°-184° C.

The combined amount of crude product (238 g) was recrystallized twicefrom toluene, after which 186 g (63%) of a white solid was obtained thathad a purity of 99.2%, determined by gas chromatography.

(d) Preparation of2-(4-carbamoylphenyl)-2-(nitrophenyl)hexafluoropropane.

198 g of 2-(4-carboxyphenyl)-2-(3-nitrophenyl) hexafluoropropaneprepared in step (c) was introduced into a mixture of 700 ml ofconcentrated sulfuric acid and 350 ml of oleum (65%). After the additionof 200 g of sulfamic acid, the reaction mixture was heated for 3 hoursat 90°-95° C. The suspension cooled to approximately 20° C. was pouredonto approximately 6 kg of ice with constant stirring. The precipitatedsolid was then filtered off and washed with water until neutral. Yield:191 g (97%) of white solid. M.p.: 147°-148° C.

(e) Preparation of4,4,-Bis[2-(3-nitrophenyl)hexafluoroisopropyl]azobenzene,

157 g of 2(4-carbamoylphenyl)-2-(3-nitrophenyl) hexafluoropropaneprepared in step (d) was introduced at 0 to 5° C. into a mixture of 900ml of 13% aqueous sodium hypochlorite solution, 150 ml of 50% sodiumhydroxide solution, and 5 ml of tricaprylmethylammonium chloride. Thesuspension was stirred for 24 hours, during which the reactiontemperature was not to exceed 50° C. The reaction mixture wasneutralized with dilute acetic acid, and the solid was filtered off andwashed with water. After recrystallization of the dried crude product(149 g), 61 g of a solid was obtained with a melting point of 185°-187°C. The workup of the mother liquor provided an additional 14 g of theproduct. Yield: 75 g (52%).

(f) Preparation of 2-(3-aminophenyl)-2-(4-aminophenyl)hexafluoropropane.

74.2 g of 4,4,-bis[2-(3-nitrophenyl)hexafluoroisopropyl]azobenzeneprepared in step (e) was dissolved in 600 ml of ethyl acetate, 1 g of 5%Pd/C was added, and the mixture was reduced with hydrogen (100 bar) inan autoclave, first at 25° C., and when the reaction subsided, at 100°C. After filtering off the catalyst, the solvent was removed. Theresidue was taken up in dilute hydrochloric acid and treated withactivated charcoal. The colorless filtrate obtained from this wasneutralized with half-concentrated ammonia solution. The precipitatethat separated was filtered off, washed with water, and dried toconstant weight. Yield: 48 g (72%) of white solid. M.p.: 142°-143° C.

EXAMPLE 2 Preparation of a polyimide of 3,4,-6F Diamine and 6FDA.

To a 100 ml three necked flask fitted with a condenser, thermometer,stirrer and under nitrogen atmosphere, 6.68 grams (0.02 mole) of2-(3-aminophenyl)-2-(4-aminophenyl) hexafluoropropane (3,4'6F Diamine)were charged along with 20 grams of distilled N-methyl pyrrolidone(NMP). The mixture was stirred until a clear solution was obtained. Tothis clear, pale yellow colored solution was added 8.88 grams (0.02mole) of 2,2-bis (3,4 dicarboxyphenyl) hexafluoropropane dianhydride(6FDA) while stirring was continued. 42 grams of NMP was then added tothe reaction mixture and agitation at room temperature was continuedovernight for a period of about 20 hours. The resulting polyamide-acid(polyamic acid) had an inherent viscosity of 0.42 dl/g, measured at 0.5g/dl at 25° C. in dimethyl acetamide.

The polyamide-acid was imidized as follows: 15.5 grams of aceticanhydride and 1.60 grams of beta-picoline are added to thepolyamide-acid solution. The reaction mixture was stirred overnight forabout 20 hours at room temperature and the resulting polyimide wasprecipitated in methanol, washed with fresh methanol and dried for 4hours in a vacuum oven at 125° C. The polymer was found to be soluble inNMP, tetrahydrofuran, acetone, MEK, diglyme, DMAC, chloroform and BLOsolvents.

EXAMPLES 3-7

Polyimides were prepared in accordance with the general procedure setforth in Example 2 by reacting the 3,4'-6F Diamine with equi-molarquantities of the following dianhydrides:

    ______________________________________                                        EXAMPLE 3:   1,2,4,5-benzene tetracarboxylic acid                                          dianhydride (PMDA),                                              EXAMPLE 4:   3,3'4,4'-diphenyl tetracarboxylic acid                                        dianhydride (BPDA),                                              EXAMPLE 5:   3,3',4,4'-benzophenone tetracarboxylic                                        acid dianhydride (BTDA),                                         EXAMPLE 6:   bis(3,4-dicarboxyphenyl) ether                                                dianhydride (ODPA).                                              EXAMPLE 7:   4,4'-bis[2-(3,4 dicarboxyphenyl)                                              hexafluoroisopropyl]diphenyl ether                                            dianhydride (12 FDA)                                             ______________________________________                                    

The inherent viscosity of each of the polyamide-acids (PA) andpolyimides (PI) produced in Examples 2-7 are reported in Table 1. Alsoreported are the glass transition temperatures (Tg°C.) as measured bydifferential scanning calorimetry and the TGA temperature in degreescentigrade at which a 5% weight loss in air is encountered. The weightaverage (Mw) and number average (Mn) molecular weights of each polyimideis also reported, as well as the dispersity factor (d) whichapproximates the Mw divided by the Mn.

                                      TABLE 1                                     __________________________________________________________________________                Inherent                                                                      Viscosity            TGA                                                      dl/gm GPC        DSC 5% wt. loss                                  Example                                                                            Dianhydride                                                                          PA PI Mw  Mn  d  Tg °C.                                                                     at °C.                                __________________________________________________________________________    2    6F-DA  0.42                                                                             0.31                                                                             42127                                                                             13864                                                                             3.11                                                                             285 520                                          3    PMDA   0.53                                                                             0.30                                                                             37651                                                                             19174                                                                             2.0                                                                              350 530                                          4    BPDA   0.69                                                                             0.42                                                                             58480                                                                             33654                                                                             1.74                                                                             296 550                                          5    BTDA   0.80                                                                             0.48                                                                             81746                                                                             52689                                                                             1.51                                                                             271 540                                          6    ODPA   0.54                                                                             0.39                                                                             57405                                                                             27253                                                                             2.1                                                                              256 550                                          7    12FDA  0.35                                                                             0.21                                                                             22340                                                                             13835                                                                             1.6                                                                              239 510                                          __________________________________________________________________________

The polyimides exhibit good solubility properties in solvents such asN-methyl pyrrolidone (NMP), dimethyl acetamide (DMAc), diglyme,methylethylketone (MEK), tetrahydrofuran (THF), acetone, chloroform,butyrolactone (BLO), dimethylsulfoxide (DMS), dimethylformamide (DMF),propylene glycol methyl ether (PGME), and the like.

This is especially significant in the case of the polyamide of Example 2(PMDA and 3,4'-6F Diamine) since the analogous polyimide based on PMDAand either 2,2-bis(3-aminophenyl) hexafluoropropane or2,2-bis(4-aminophenyl) hexafluoropropane are not soluble or are onlysparingly soluble in such solvents.

The polyimides also exhibit improved thermal flow properties and may bemelt spun to form fibers and filaments. Because of their good solubilityin common organic solvents, films may be cast from solvent solutions.Such films may be used as printed circuit backings, insulatingdielectric interlayers and other applications where tough, hightemperature stable films having good dielectric properties have beenused in the past.

The polyimides of this invention may be molded using standard techniquessuch as compression molding or injection molding to produce meltfabricated articles such as safety masks, windshields, electroniccircuit substrates, airplane windows or the like. They may be compoundedwith graphite, graphite fiber, molybdenum disulphide or PTFE for theproduction of self-lubricating wear surfaces useful for piston rings,valve seats, bearings and seals. They may also be compounded with fiberssuch as glass, graphite or boron fibers to produce molding compounds forhigh strength structural components such as jet engine components. Thepolyimides may also be compounded with friction materials to producemolding compounds for high temperature braking components or withabrasive materials such as diamonds for high speed grinding wheels.

The polyimides may be cast as films useful as wire and cable wraps,motor slot liners or flexible printed circuit substrates. They may beused as coatings on substrates such as aluminum or silicone dioxide.They are also useful to produce high temperature coatings for magneticwire, dip coatings for various electronic components, protectivecoatings over glass, metal and plastic substrates, wear coatings, andphotoresist coatings useful in microelectronic processing.

The polyimides may also be used to produce high temperature adhesivesfor bonding aerospace structures or electrical circuitry, conductiveadhesives when mixed with conductive fillers such as silver or gold formicroelectronic applications, or adhesives for glass, metal or plasticsubstrates.

The polyimides may also be used as varnish compositions or matrix resinsto produce composites and laminates. The varnish compositions and matrixresins may be used to impregnate glass or quartz cloth, or graphite orboron fibers, for the production of radomes, printed circuit boards,radioactive waste containers, turbine blades, aerospace structuralcomponents or other structural components requiring high temperatureperformance, non-flammability and excellent electrical properties.

In general, the polyimides and polyamide-acid precursors of thisinvention may be used in all applications as disclosed in copendingapplication Ser. No. 124,704, filed in the U.S. Patent and TrademarkOffice on Nov. 24, 1987, the disclosure of which application isincorporated herein by reference.

It is to be understood that the above described embodiments of theinvention are illustrative only and that modifications throughout mayoccur to those skilled in the art. Accordingly, this invention is not tobe regarded as limited to the embodiments disclosed herein, but is to belimited as defined by the appended claims.

What we claim is:
 1. A polyimide polymer comprising recurring groups having the structure: ##STR3## wherein n is the number of repeating groups, R is a tetravalent aromatic organic radical, and Q is the residuum having the formula: ##STR4##
 2. The polymer of claim 1 wherein R is selected from the group consisting of phenylene, naphthalene, a bis-phenylene compound and mixtures thereof, which may be unsubstituted or ring substituted with a radical selected from the group consisting of halogen, hydroxy, lower C₁ to C₆ alkyl and lower C₁ to C₆ alkoxy.
 3. The polymer of claim 1 wherein n is a number sufficient to provide an inherent viscosity of at least about 0.2 dl/g as measured from a solution of the polymer in dimethylacetamide at 25° C. at a polymer concentration of 0.5 weight percent.
 4. The polymer of claim 1 prepared by forming the amide-acid condensation product of 2-(3-aminophenyl)-2-(4-aminophenyl) hexafluoropropane with an aromatic dianhydride and imidizing said amide-acid condensation product.
 5. The polymer of claim 4 wherein said aromatic dianhydride is selected from the group consisting of bis (3,4-dicarboxyphenyl) ether dianhydride, 3,3',4,4'benzophenone tetracarboxylic dianhydride, 3,3',4,4'-diphenyl tetracarboxylic acid dianhydride, 2,2-bis (3,4 dicarboxy phenyl) hexafluoropropane dianhydride, 1,2,4,5-benzene tetracarboxylic acid dianhydride, and 4,4'-bis[2-(3,4-dicarboxyphenyl) hexafluoroisopropyl]diphenyl ether dianhydride.
 6. The polymer of claim 4 wherein said amide-acid condensation includes a mixture of said 2-(3-aminophenyl)-2-(4-aminophenyl) hexafluoropropane with at least one other diamine having the formula:

    NH.sub.2 --Y--NH.sub.2

wherein Y is an aromatic moiety.
 7. The polymer of claim 5 wherein n is a number sufficient to provide an inherent viscosity of at least about 0.2 dl/g as measured from a solution of the polymer in dimethylacetamide at 25° C. at a polymer concentration of 0.5 weight percent.
 8. The polymer of claim 7 wherein said dianhydride is 2,2-bis (3,4 dicarboxyphenyl) hexafluoropropane dianhydride.
 9. The polymer of claim 8 wherein said diamine and said dianhydride are reacted in equi-molar amounts.
 10. The polyimide of claim 1 dissolved in organic solvent.
 11. A fiber comprising the polyimide of claim
 1. 12. A film comprising the polyimide of claim
 1. 13. A compression molded shaped article comprising the polyimide of claim
 1. 